1. Field of the Invention
The present invention relates to door locks and, more particularly, to a tubular latch assembly for use with handlesets or the like that is operable by movement of an opener such as a thumbpiece or the like.
2. Background of the Invention
Main entry doors on commercial and residential buildings are often equipped with exterior “handlesets”, which consist of a handle or “pull” mounted on an escutcheon plate and a thumbpiece for operating the lock mechanism mounted above the handle, in such a way that the thumbpiece can be operated with the thumb while grasping the handle. Although a number of different lock mechanisms may be equipped with handlesets, the types known as tubular, or “bored through” locksets have become virtually universal in residential applications. Tubular handlesets are designed to be installed in an industry standard pattern of holes drilled in the edge and face of the door. Compared to traditional door preparation methods, such as cutting mortise pocket in the door edge, drilled door preps require substantially less time and skill. Unfortunately, they also impose constraints on the space available for the operating mechanism of the lock, and consequently make the mechanical design of the mechanism more difficult.
Latches are usually designed so that the latch bolt is retracted by the action of a slide bar that interacts with cams projecting from a hub or pair of hubs that rotate on an axis perpendicular to the direction of movement of the latch bolt. Other arrangements exist, but all work according to the same basic principle. The hubs are typically activated by a spindle attached to a knob or lever on the inside of the door, with an axis of rotation that is aligned with the axis of rotation of the latch hubs. When the latch is actuated by a handleset, however, the motion of the thumbpiece is essentially a vertical motion that acts perpendicular to the plane formed by the line of movement of the bolt and the axis of rotation of the hubs. A motion translator is therefore required to change the movement of the thumbpiece into a rotational motion that can be used to drive the latch hubs. So typically, the latch of a tubular handleset is operated by a spindle connected to a knob or lever on the inside and a spindle attached to a motion translator driven by the thumbpiece from the outside. In most cases, the latch has two hubs, one operated by each spindle, so that the inside and outside trims operate independently.
Another design issue in tubular handlesets is that, while it is desirable for a knob or lever to have 45 degrees or less rotation to assure a comfortable range of hand motion, reducing the hub rotation imposes unacceptably high load requirements at the thumbpiece, which is smaller than the knob or lever, making it more difficult to apply a force necessary to operate the latch. This is especially true in situations where there is a warped door or tight weather stripping. In addition to affecting the effort required to operate the thumbpiece, forces experienced by the components of the motion translator are high, increasing internal friction and making the components more likely to break. The problem may be overcome by making the range of movement of the thumbpiece very large, but that is undesirable for both mechanical and ergonomic reasons.
Another effect of using a motion translator between the thumbpiece and the latch is an increase in the number of components in the lockset. For example, FIG. 22 is a prior art illustration from U.S. Pat. No. 5,513,510 to Solovieff et al. showing an exemplary handleset with thumbpiece and rack that requires a motion translation mechanism, and particularly gear pieces 52, 56 to change the vertical motion of the thumbpiece 10 to the rotary motion of the latch hub 66. Referring to FIG. 22, it can be seen that item 32, 33, 52 and 58 are required only for translation of the motion of thumbpiece 10 to rotation to operate latch 80. These components add cost, both in the cost of the component itself and added assembly cost of the mechanism. They also increase internal friction through contact between the parts and in the bearings and surfaces required to guide them, and decrease reliability as the parts are small and are difficult to manufacture and assemble correctly.
It would be greatly advantageous to provide a latch that allows for direct actuation by a thumbpiece (or other opener) without an intervening motion translation mechanism. It would also be desirable to have such a latch that could also be independently actuated by a spindle attached to a knob or lever, and which could be operated in either direction to accommodate use with knobs or, in the case of levers, both left hand and right hand operation.